The Effects of Ring Types of Typical Cycloparaffins and Aromatics Presented in Biofuels to the Sooting Tendency and Freezing Point

This study aims to investigate the effects of the structure and number of rings of two types of hydrocarbons (cycloparaffins and aromatics) on the sooting tendency and the freezing point when blended with paraffins. Hexylcyclohexane and hexylbenzene were selected to represent for single ring while bicyclohexyl represented double saturated rings of cycloparaffins, respectively. In addition, cyclohexylbenzene was chosen to represent for hydrocarbons consisting of both cycloparaffin and aromatic rings. These ring hydrocarbons were blended with dodecane, which is used as a surrogate for paraffins in biojet fuels, to test for smoke point and freezing point properties by using the ASTM D1322 and ASTM D2386. The results show that increasing rings in each hydrocarbon class leads to a decrease in smoke point while increasing significantly the freezing point. On the other hand, the increase in cyclo-rings has lower negative effects on both the smoke point and freezing point as compared with aromatic rings. From this study, it could be concluded that the multi-ring in hydrocarbons has negative effects on both properties, especially, on the freezing point, thus they are unexpected to be included in the biojet fuels.